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package org.apache.juneau.rest.vars;

import org.apache.juneau.*;
import org.apache.juneau.rest.*;
import org.apache.juneau.rest.annotation.*;
import org.apache.juneau.svl.*;

/**
 * URL variable resolver.
 * 
 * <p>
 * The format for this var is <js>"$U{uri}"</js>.
 * 
 * <p>
 * The advantage of using this variable is that you can resolve URLs with special protocols such as
 * <js>"servlet:/xxx"</js>.
 * 
 * <p>
 * See {@link UriResolver} for the kinds of URIs that can be resolved.
 * <ul>
 * 	<li>{@link HtmlDoc#widgets() @HtmlDoc.widgets()}
 * </ul>
 * 
 * <p>
 * Uses the URI resolver returned by {@link RestRequest#getUriResolver(UriResolution, UriRelativity)} with resolution
 * {@link UriResolution#ROOT_RELATIVE} and relativity {@link UriRelativity#RESOURCE}.
 * 
 * <h5 class='section'>See Also:</h5>
 * <ul>
 * 	<li class='link'><a class="doclink" href="../../../../../overview-summary.html#juneau-rest-server.SvlVariables">Overview &gt; juneau-rest-server &gt; SVL Variables</a>
 * </ul>
 */
public class UrlVar extends SimpleVar {

	private static final String SESSION_req = "req";

	/** The name of this variable. */
	public static final String NAME = "U";

	/**
	 * Constructor.
	 */
	public UrlVar() {
		super(NAME);
	}

	@Override /* Parameter */
	public String resolve(VarResolverSession session, String key) {
		RestRequest req = session.getSessionObject(RestRequest.class, SESSION_req);
		return req.getUriResolver().resolve(key);
	}
}